Oxygen budgets in subtidal arctic (Kongsfjorden, Svalbard) and temperate (Helgoland, North Sea) microphytobenthic communities

Abstract

We compared primary production and respiration of temperate (Helgoland, North Sea) and subtidal Arctic (Kongsfjorden, Svalbard) microphytobenthic communities during summer. The diatom communities were generally characterized as cosmopolitan, displayed no site specificity, and had similar chl a and fucoxanthin concentrations. Their net and gross photosynthesis rates and light adaptation intensities, derived from laboratory microsensor measurements, were also similar, despite differences in water temperature. Daily oxygen fluxes across the sediment−water interface were estimated by combining laboratory microprofile and planar optode measurements with in situ data on oxygen penetration and light dynamics. During the study period, the Svalbard sediments were on average net heterotrophic, while the Helgoland sediments were net autotrophic (−22.4 vs. 9.2 mmol O 2 m −2 d −1). This was due to high infaunal abundance in the Svalbard sediments that caused high oxygen uptake rates in the sediments and consumption below the sediment euphotic zone. Additionally, bioirrigation of the sediment due to infaunal burrow ventilation was reduced by light; thus, the sedimentary oxygen inventory was reduced with increasing light. Conversely, light-enhanced the oxygen inventory in the Helgoland sediments. Oxygen dynamics in the Svalbard sediments were therefore dominated by bioirrigation, whereas in the Helgoland sediments they were dominated by photosynthetic oxygen production.

Contribution towards a morphological and molecular taxonomic reference library of benthic marine diatoms from two Arctic fjords on Svalbard (Norway)

“…Recent investigations in Kongsfjorden on benthic diatoms from soft bottom and seaweed surfaces provided the first floristic list. So far, a total of at least 69 diatoms species were reported based on morphological features, and these data form a first baseline for a high-latitude fjord system (Sevilgen et al 2014;Fredriksen et al 2015). When interpreting the species lists provided in both publications, biodiversity seems to be relatively low compared to other marine shallowwater areas of temperate regions.…”

“…In addition, diatoms are responsible for 25 % of global CO 2 fixation (Smetacek 1999) and contribute to 45-50 % to the marine primary production (Mann 1999;Yool and Tyrrell 2003). Studies on microphytobenthic communities in polar regions are still rare, but the very few show high rates of primary production which can be compared with those in temperate regions (Glud et al 2002(Glud et al , 2009Woelfel et al 2010Woelfel et al , 2014Sevilgen et al 2014). Furthermore, the microphytobenthos is a key component in polar trophic food webs.…”

“…Most microphytobenthic studies on Svalbard focused so far on the entire diatom community, on their primary production rates and chlorophyll ratios (Woelfel et al , 2010(Woelfel et al , 2014Sevilgen et al 2014). But also some experiments on the physiological performance of individual Arctic benthic diatoms were undertaken (Karsten et al 2006(Karsten et al , 2012Schlie et al 2011) and are still in progress in Rostock laboratories.…”

“…In one recent study and a review undertaken in the Arctic Kongsfjorden on Svalbard (Norway) (Sevilgen et al 2014;Fredriksen et al 2015), it was possible to identify at least 69 benthic diatom species from the microphytobenthos community taken in sediment cores. A diverse diatom community was reported at different stations of the fjord, as well as community changes over time.…”

Survival of early life history stages of Arctic kelps (Kongsfjorden, Svalbard) under multifactorial global change scenarios

“…At Hansneset, Kongsfjorden, mean summer sea water temperatures at 5 m depth range between 4 and 6°C (Svendsen et al 2002;Sevilgen et al 2014). These data were used to simulate our ambient temperature treatment (4 and 5°C, respectively).…”